Patent EA-005232-B1 (EA)
Title: A method and apparatus for processing seismic data
Inventor: ROBERTSSON JOHAN
IPC: G01V1/36
Filed: 2001-12-07
Abstract: 1. A method of processing multi-component seismic data acquired at a receiver, the method comprising the steps of: a) decomposing a first portion of the seismic data into a plurality of wavefield components using a first decomposition scheme; b) selecting first and second wavefield components that should not have arrived simultaneously at the receiver; and c) multiplying the first wavefield component by the second wavefield component, d) adjusting, at least, one parameter of the decomposition scheme on the basis of the result of step (c). 2. A method as claimed in claim 1, wherein in step (d) at least one parameter being adjusted of the decomposition scheme if the result of step (c) is significantly different from zero. 3. A method as claimed in claim 2 and further comprising decomposing the first portion of the seismic data into a plurality of wavefield components using the adjusted decomposition scheme. 4. A method as claimed in claim 4 and further comprising repeating step (b) and step (c). 5. A method as claimed in any preceding claim and comprising the further steps of: e) selecting third and fourth wavefield components that should not have arrived simultaneously at the receiver; and f) multiplying the third wavefield component by the fourth wavefield component. 6. A method as claimed in any preceding claim further outputting the parameters of the adjusted decomposition scheme. 7. A method as claimed in claim 2 or in any of claims 3 to 6, wherein step (d) comprises adjusting a parameter of the decomposition scheme indicative of the seismic properties of a layer at or near the earth's surface. 8. A method as claimed in claim 2 or in any of claims 3 to 6, wherein step (d) comprises adjusting a parameter of the decomposition scheme indicative of the receiver calibration. 9. A method as claimed in any preceding claim further comprising the step of processing a second portion of the seismic data using the adjusted decomposition scheme. 10. A method as claimed in claim 1 and further comprising the steps of: g) decomposing the first portion of the seismic data into a plurality of wavefield components using a second decomposition scheme; h) multiplying the first selected wavefield component obtained in step (g) by the second selected wavefield component obtained in step (g); and i) comparing the result of step (c) with the result of step (h). 11. A method as claimed in claim 10 and further comprising selecting either the first decomposition scheme or the second decomposition scheme on the basis of the result of step (i). 12. A method as claimed in claim 11 further comprising the step of processing a second portion of the seismic data using the selected decomposition scheme. 13. A method as claimed in any preceding claim wherein step (c) or step (f) comprises computing: wherein alpha (i,j) and beta (i,j) are the first and second wavefield components, the sum over (i) is a sum over time samples, Nt is the number of time samples used for the inversion, the sum over (j) is a sum over traces, offsets, or receivers, Nx is the number of traces, offsets, or receivers used for the inversion, and E is energy, i,j- integers, t- time. 14. A method as claimed in any of claims 1 to 13 wherein step (c) or step (f) comprises computing: wherein alpha (i,j) and beta (i,j) are the first and second wavefield components, the sum over (i) is a sum over time samples, Nt is the number of time samples used for the inversion, the sum over (j) is a sum over traces, offsets, or receivers, Nx is the number of traces, offsets, or receivers used for the inversion, and E is energy, i,j- integers, t- time. 15. A method as claimed in any of claims 1 to 13 and performed in the frequency-wavenumber domain. 16. A method of acquiring and processing multi-component seismic data comprising the steps of acquiring multi-component seismic data at a receiver; and processing the seismic data comprising the steps of: a) decomposing a first portion of the seismic data into a plurality of wavefield components using a first decomposition scheme; b) selecting from wavefield components obtained in step (a) first and second wavefield components that should not have arrived simultaneously at the receiver; and c) multiplying the first wavefield component by the second wavefield component, d) adjusting, at least, one parameter of the decomposition scheme on the basis of the result of step (c). 17. An apparatus for processing multi-component seismic data acquired at a receiver, the apparatus comprising: a) first decomposition means for decomposing a first portion of the seismic data into a plurality of wavefield components using a first decomposition scheme; b) means for selecting from wavefield components obtained in step (a) first and second wavefield components that should not have arrived simultaneously at the receiver; and c) means for multiplying the first wavefield component by the second wavefield component, (d) means for adjusting at least one parameter of the decomposition scheme on the basis of the result of multiplying the first wavefield component by the second wavefield component. 18. An apparatus as claimed in claim 17 wherein the adjusting means are adapted to adjust one or more parameters of the decomposition scheme if the result of multiplying the first wavefield component by the second wavefield component is significantly different from zero. 19. An apparatus as claimed in claim 18 wherein the first decomposition means are adapted to decompose the first portion of the seismic data into a plurality of wavefield components using the adjusted decomposition scheme. 20. An apparatus as claimed in any of claims 17 to 19 and comprising e) means for selecting third and fourth wavefield components that should not have arrived simultaneously at the receiver; and f) means for multiplying the third wavefield component by the fourth wavefield component. 21. An apparatus as claimed in any of claims 18 to 20 and further comprising output means for outputting the parameters of the adjusted decomposition scheme. 22. An apparatus as claimed in any of claims 18 to 21 and further comprising means for processing a second portion of the seismic data using the adjusted decomposition scheme. 23. An apparatus as claimed in claim 17 and further comprising: g) second decomposition means for decomposing the first portion of the seismic data into a plurality of wavefield components using a second decomposition scheme; h) means for multiplying the first selected wavefield component obtained by the second decomposition means by the second selected wavefield component obtained by the second decomposition means; and i) means for comparing the result of multiplying the first wavefield component by the second wavefield component with the result of multiplying the first selected wavefield component obtained by the second decomposition means by the second selected wavefield component obtained by the second decomposition means. 24. An apparatus as claimed in claim 23 and further comprising means for selecting either the first decomposition scheme or the second decomposition scheme on the basis of the result of the result from the comparing means. 25. An apparatus as claimed in claim 24 and further comprising means for processing a second portion of the seismic data using the selected decomposition scheme. 26. An apparatus as claimed in any of claims 17 to 25 and comprising a programmable data processor. 27. A storage medium containing a program for a data processor of an apparatus comprising a) first decomposition means for decomposing a first portion of the seismic data into a plurality of wavefield components using a first decomposition scheme; b) means for selecting from wavefield components obtained in step (a) first and second wavefield components that should not have arrived simultaneously at the receiver; and c) means for multiplying the first wavefield component by the second wavefield component, (d) means for adjusting at least one parameter of the decomposition scheme on the basis of the result of multiplying the first wavefield component by the second wavefield component. 18. An apparatus as claimed in claim 17 wherein the adjusting means are adapted to adjust one or more parameters of the decomposition scheme if the result of multiplying the first wavefield component by the second wavefield component is significantly different from zero.